1. Field of the Invention
The invention relates to a tourbillon for a timepiece, having a setting device for setting the hands of the timepiece, having a circular balance wheel, which can be pivoted about a pivot pin, and with an escapement comprising a pallet and escapement wheel. The balance wheel and the escapement are arranged on a base plate and a balance staff of the balance wheel is mounted in a rotatable manner, by way of one end, on the base plate and, by way of its other end, on a cage which encloses the balance wheel in a basket-like manner and which has, outside the radially circulating periphery of the balance wheel, a plurality of pillars spaced apart from one another on the base plate and forms, together with the base plate, a rotary mount which is fixed to the seconds drive of the timepiece and can be driven in a rotatable manner, by means of said drive, about a swivel pin which is coaxial with the pivot pin.
2. Description of the Prior Art
Tourbillons of the type mentioned in the introduction are known.
It is also known, in the case of timepieces without a tourbillon, that, for setting the minute hand, the balance wheel is arrested by a spring arm, which is pivoted for abutment against the balance wheel, and, following completion of the operation of setting the hands, the act of pivoting the spring arm away from the balance wheel releases the latter again from its arrested state.
It is not possible to use such an arresting action of the balance wheel in timepieces with a tourbillon, since this results in the stationary spring arm colliding with the circulating cage of the tourbillon.